The importance of automatic identification systems increases particularly in the service sector, in the field of logistics, in the field of commerce and in the field of industrial production. Further applications of identification systems are related to the identification of persons and animals.
In particular contactless identification systems like transponder systems (for instance using an RFID tag) are suitable for a wireless transmission of data in a fast manner and without cable connections that may be disturbing. Such systems use the emission and reflection/absorption of electromagnetic waves, particularly in the high frequency domain.
For certain RFID applications, it may be required to realize two different power-modes with an RFID integrated circuit (IC). A Low Power Mode may be used requiring low current consumption of the IC. Hence, high read-ranges of the RFID-Tag may be possible. A High Power Mode may be used for applications, where an extended functionality of the IC is required, resulting in an increased current consumption of the IC. There may be two reasons for that. First, the IC itself consumes more current due to extended functionality in the digital or analog part. Second, the IC is supplying current to an externally connected load, another IC or something else, like an actuator. Currently existing tag-designs only have a certain setting of center-frequency, frequency response, bandwidth and quality-factor. Hence the RFID-Tag only has a certain application specific performance depending on these parameters and it is not possible for the tag to react on specific needs of the application like close coupled tags or tags on different types of materials.
U.S. 2005/024187 discloses a radio frequency (RF) communication device comprising means for switching between a low current operating mode and a high current operating mode. The low current operating mode is optimized to conserve power while the RF device is awaiting a wake-up signal from an interrogator. The high current operating mode is optimized to provide antenna matching during backscatter communications so as to maximize the range of backscatter communication between the RF device and the interrogator.
U.S. 2008/136643 discloses an apparatus receiving a radio frequency (RF) signal transmitted from a Radio Frequency Identification (RFID) reader. The apparatus measures the strength of the received RF signal, and controls the power supplied from the power supply unit included in the tag or the power excited by the RF signal to be supplied to the tag according to whether the power excited by the received RF signal exceeds a level necessary to operate the tag based on the measured strength of the RF signal.
U.S. 2008/311861 discloses a transponder comprising a capacitor for storing power transmitted via an air interface and an arithmetic logic unit that can be supplied with the stored power. A capacitor voltage of the capacitor is compared with a first threshold and with a second threshold, whereby the first threshold and the second threshold are different. In a first operating mode, when the capacitor voltage is above the first threshold, the arithmetic logic unit performs a number of routines with a different priority. In a second operating mode, when the capacitor voltage is between the first threshold and the second threshold, a number of low-priority routines are stopped and a number of high-priority routines are continued.